KINETIC OF COOKING PARBOILED PRE-GERMINATED BROWN RICE AND TTI DEVELOPMENT

บทคัดย่อ

Parboiled pre-germinated brown rice (PPGBR) is a modified rice by germinating and parboiling to improve its quality. It is considered health benefit as the results of hydrolysis of high molecular weight polymers which decreased the molecular size and produced bio-functional substances during germination. Normally, the qualities of cooked rice depend on many factors; cooking condition is one of them.  The purpose of this work is to determine the activation energy (E_a) of rice cooking process and develop the time-temperature indicator (TTI) for monitoring the process. Rice cooking kinetic of PPGBR from KDML 105 was determined by measuring the hardness value of cooked rice over time. The optimum cooking time at 100°C was 20 min. The E_a of rice cooking, derived from Arrhenius plots of cooking rate constant was 16.69 kJ/mole. TTI was developed based on chemical reaction to monitor rice quality during processing. The absorbance at 420 nm was measured over time at 80°C, 90°C and 100°C. The color of TTI changed from colorless to dark brown. The E_a of TTI calculated from Arrenius equation was 94.30 kJ/mol. The color changing of TTI directly related to rice cooking at 100°C. The present results suggest that the color changing of TTI could be used as an indicator to monitor cooked rice quality by visual checking.